Alkali metal phenoxide complex

These studies, which employed density functional theory (DFT) methods (B3LYP/LANL2DZ/Gaussian 98) proposed that the reactions of all alkali metal phenoxides with C02 followed a similar ground mechanism that comprised three intermediates and three transition states. In step 1, C02 must first be activated by an alkali metal phenoxide. In the case of the sodium phenoxide [24a], C02 can only attack at the polarized O-Na bond to form a Ph0Na/C02 complex as the first intermediate (structure 4). The calculation definitely rules out a direct C-C bond formation at the aromatic ring. 

Structures of [alkali metal phenoxide C02] complex In the Kolbe-Schmitt reaction, phenyl carbonate (I) was originally proposed as the intermediate[2], but infrared absorption (i.r.) spectra of the intermediate showed a band at 1684 cm which disagrees with I, because an absorption band at 1754 cm of methyl phenyl carbonate is not much different from 1748 cm for dimethyl carbonate.[3] Therefore, the carbonyl of the complex might be in the structures such as (II) - (IV). 

The mechanism of the Kolbe-Schmitt reaction was investigated since the late 1800s, but the mechanism of the carboxylation could not be elucidated for more than 100 years. For a long time, the accepted mechanism was that the carbon dioxide initially forms an alkali metal phenoxide-C02 complex, which is then converted to the aromatic carboxylate at elevated temperature. The detailed mechanistic study conducted by Y. Kosugi et al. revealed that this complex is actually not an intermediate in the reaction, since the carefully prepared phenoxide-C02 complex started to decompose to afford phenoxide above 90 °C. They also demonstrated that the carboxylated products were thermally stable even at around 200 °C. The CO2 electrophile attacks the ring directly to afford the corresponding ortho- or para-substituted products. (When the counterion is large (e.g., cesium) the attack of CO2 at the ortho-position is hindered therefore, the para-substituted product is the major product.)... 

Metalation of calix[4]arene with NbClj and TaClj produces metal complexes which, when treated with alkali phenoxides, entrap the alkali metal ions within the calix, as indicated by X-ray crystallography Zanotti-Gerosa, A. Solari, E. Giannini, L. Floriani, C. Chiesi-Villa, A. Rizzoli, C. J. Chem. Soc., Chem. Commun. 1997, 183. 

Complexes containing alkali metal are formed in the interaction of LuClj with sodium or lithium phenoxides [22, 110]. Depending on the stoichiometry of initial reagents one, two or all chlorine atoms can be substituted with RO groups ... 

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